Gas turbine engines typically include a compressor for compressing incoming air, a combustor for mixing fuel with the compressed air and igniting the fuel/air mixture to produce a high temperature gas stream, and a turbine section that is driven by the high temperature gas stream. The amount of fuel required to generate an observed power level defines the efficiency of the system. However, in many known gas turbine systems, the accuracy of the fuel flow measurement is not adequate for detailed performance assessments.